Artillery computer



Filed Feb. 19, 1944 3 Sheets-Sheet 1 FIG. 2

X AXIS INVENTOR E LAKATO-S ATTORNEY Nov. 29, 1949 Filed Feb. 19, 1944 FIG. 3

E. LAKATOS ARTILLERY COMPUTER 3 Sheets-Sheet 2 //v VEN TOR E. LAKA 705 A TTORNEV Patented Nov. 29, 1949 UNITED STATES PATENT OFFICE Telephone Laboratories,

Incorporated, New

York, N. Y., a corporation of New York Application February 19, 1944, Serial N 0. 523,171

9 Claims.

This invention relates to artillery computers and particularly to computers in which some of the data are represented by electrical quantities.

The object of the invention is a method and means for computing and indicating the deflection angle, or angle at the gun by which the line of fire leads the present position of the target.

In the drawings:

Fig. 1 discloses a prediction system;

Fig. 2 shows the geometrical relationships involved;

Fig. -3 discloses a ballistic correction system associated with the system of Fig. 1;

Figs. 4A, 4B, 4C disclose alternative forms of the invention associated with the system of Fig. 3;

Fig. 5 shows a phase controlling network used in the systems of Figs. 3, 4A, 4B, 40;

Fig. 6 shows a smoothing network used in the system of Fig. 1; and

Fig. 7 shows a summing amplifier used in the systems of Figs. 1, 3, 4A, 4B, 4C.

In Fig. 2, the line To, Tp represents the course of a moving target. From an observation station 0, the distance 0T0 and the azimuth ATO, between the South axis and the line 0T0, are continuously measured. These observations are transmitted to the computer, and from them and the known coordinates of the gun with respect to the point of observation the computer continuously produces electrical quantities proportional to the rectangular coordinates, X0 and Y0, from the gun to the target. From these coordinates and the rates of change of these coordinates, the computer approximately determines the values of the coordinates of the position of the target at which a hit is predicted, and also selects the values of the range and azimuth of the line of fire to a virtual target that, corrected for ballistic range and deflection effects will cause a shell to hit approximately at the predicted position of the target. The two values for the predicted position of the target are automatically compared and, if there is a discrepancy, the values of both approximations are changed to produce coincidence of the predicted positions at the correct value.

In Fig. 2, T1: is the correct predicted position of the target. The range and azimuth of the line of fire is directed to a virtual target Tv such that the shell, fired at Ty and influenced by the total .ballistic range effects SR. and the total ballistic deflection effects SD will burst at Tp. In the present disclosure, ballistic efiects which increase therange are represented by positive quantities and ballistic effects which deflect the shell to 2 the left of the virtual position of the target are also represented by positive quantities. The total range R SR may be designated as the firing range RF. The firing range RF is usually comparable with, but slightly less than the map range GT The azimuth AF of the line of fire GT: is, as usual, in terms of the angle traced clockwise from the South. The angle B 270 AF. Let angle ToGTf be AD the angle of deflection, that is, the angle by which the line of fire leads the present position of the target.

First method Draw To parallel to the Y axis, then Tof Y0 and GI X0.

tan (AD+B) o 1 tan AD: X 5 czs B iY z sfi B X sin AF-l-Y cos AF tan AD.X0 sin AF+tan AD.Y0 cos AF+XO cos AF-Yo sin AF=0 (1) Second method T.,h tan AD- SDDX cos AF+DY sin AF X0 sin AF+Y, cos AF tan AD X sin AF+Y0 cos AF) +SD .DX cos AF+DY sin AF=0 (2) Third method DX cos AF+DY sinAF-l-SD Rf+DX sin AF+DY cos AF AD.R +tan AD(DX sin AF+DY cos AF) SD-i-DX cos AFDY sin AF= (3) In Fig. 2 Tog=Yo cos B; hg=ef=Xo sin B, thus Yo cos BXo sin B=T0h,=+Xo cos AFY0 sin AF, the rectangular coordinate of the present position of the target with respect to the gun perpendicular to the line of fire.

Also Ge=Xo cos B; jg=eh=Yo sin B, thus X0 cos B+Yo sin B GhE(Xo sin AF+YO cos AF,) the rectangular coordinate of the present position of the target with respect to the gun in the line of fire.

T0h=aT =ab+bT T;T -=DX sin BDY cos B+.S'D=DX cos AF+DY sin AF+SD, the rectangular coordinate of the present position of the target with respect to the gun, perpendicular to the line of fire.

cos BDY sin B=R+DX sin AF+DY cos AF, the rectangular coordinate of the present position of the target with respect to the gun in the line of fire.

Thus, in each of the three methods, the tangent of the deflection angle is equal to the quotient of the rectangular coordinate of the present position of the target with respect to the gun perpendicular to the line of fire and the rectangular coordinate of the present position of the target with respect to the gun in the line of fire.

The present computer is primarily intended for the control of substantially horizontal fire, such as coast defense fire against maritime vessels or land fire against vehicles. The target is continuously observed by known means, such as a simple theodolite and a range finder.

The observations of the distance to and azimuth of the present position of the target are continuously transmitted to the computer by some convenient data transmission system, such as the system shown in U. S. Patent 1,483,235, February 12, 1924, R. V. Morse. The complete data may be transmitted by such a system, or, for

tan AD= tan greater accuracy, the even hundreds of yards of distance and degrees of azimuth may be telephoned to the operator of the computer at regular intervals, and the divisions of the hundreds of yards and degrees transmitted by the data transmission system.

In Fig. 1, the potentiometer I is the receivin potentiometer of the distance data transmission system. A constant speed motor 2 drives the shaft 3 through the variable speed drive 4, of any suitable type, such as the drive shown in U. S. Patent 1,448,490, March 13, 1923, H. Moakley. In this drive the motor 2 drives a disc which, through an interposed ball, drives a cylinder fixed to shaft 3. The speed ratio is determined by the position of the ball on the disc.

The position of the ball is varied by the rack and pinion 5, attached to the ball race and adjusted through the gears 6 by the hand-wheel 7.

The shaft 3 drives the shaft 9, rotating the brush of potentiometer I, through a differential gear 8. The ring gear of differential gear 8 may be rotated by the hand-wheel 1,

Rotation of the hand-wheel I will thus cause an angular movement of the brush of potentiometer l and will also change the speed of shaft 9.

The operator adjusts the hand-wheel 7 to balance the data transmission system and set the speed of the brush of potentiometer l to maintain the system balanced, as indicated by the meter l0.

Potentiometer II is the'receiving potentiometer of the azimuth data transmission system. The brush of potentiometer I l is driven by motor l2 under the control of hand-wheel l1, and unbalance of this system is indicated by meter 20.

Elements [3, I4, l5, l6, l8, l9 operate similarly to elements 3, 4, 5, 6, 8, 9.

A source of voltage 2|, having its positive pole grounded, is connected across the winding of potentiometer 22. The brush of potentiometer 22 is rotated by shaft 9 to select a voltage proportional to the distance to the present position of the target, 0T0, Fig. 2.

In order to show the circuit connections more clearly, the potentiometers I and 22 have been shown as if they were rotated degrees with respect to the shaft 9. The other potentiometers in the system have been similarly rotated with respect to the shafts rotating the brushes.

The windings of all the potentiometers in the system may conveniently be in the form of close even windings of resistance wire on thin fiat cards having one straight edge. The card is supported in the arc of a circle concentric with the shaft driving the brushes. The resistance wire is bared on the straight edge of the card to form a good contact for the brush. The other edge of the card is shaped so that the width of the card will vary in such manner as to produce the desired variation of the voltage selected by the brush with the angular position of the brush. The width of the card will vary approximately as the derivative of the voltage function, corrected, if necessary, for the load connected to the brushes.

Potentiometers which vary during a run have been represented by circular potentiometers; and potentiometers which are handset to a constant value by straight potentiometers. The handset potentiometers may also be circular, if desired.

The voltage selected by the brush of potentiometer 22 is applied through resistor 23 to the input circuit of an amplifier 24 having a feedback resistor 25. The amplifier 24 may be any stable high gain amplifier, such as the amplifier shown in Fig. 7.

The amplifier shown in Fig. 7 is of the type shown in United States Patent 2,401,779, June 11, 1946, by K. D. Swartzel and assigned to the assignee of the present application. The amplifier may conveniently include three high gain vacuum tubes 3|, 32, 33, coupled by any suitable interstage networks, such as the networks shown 'in U. S. Patent 1,751,527, March 25, 1930, H. Nyquist. Though for convenience, the vacuum tubes 3 I, 32, 33 have been shown as triodes, other types of tubes, such as pentodes, may be used with appropriate changes in the power supplies.

The negative pole of a source of voltage 34 is connected to the cathode of vacuum tube 33 and the positive pole grounded. The positive pole of a source of voltage 35, having its negative pole grounded, is connected through resistor 36 to the anode of vacuum tube 33. The voltages of the sources 34, 35, and the resistances of resistor 36 weal H i ggsgeor and the anode-cathode path of vacuum tube 33 are adjusted so that,-in the absence of an applied signal, they form a balanced bridge, and no voltage is supplied to the output circuit.

If a source of positive voltage 31 be connected through a resistor 23 to the control grid of vacuum tube 3|, it will tend to make the control grid of vacuum tube 3| positive with respect to ground, thus tending to make the control grid of vacuum tube 32 negative with respect to.

ground and the control grid of vacuum tube 33 positive with respect to ground. The positivevoltage on the control grid of vacuum tube 33 will reduce the resistance of the anode-cathode path of vacuum tube 33, increasing the current flowing in the vacuum tube 33 and resistor 36, unbalancing the bridge and applying a negative voltage to the output terminals and load. Similarly, a negative voltage applied to the control.

grid of vacuum tube 3| will tend to make the control grid of vacuum tube 33 negative with respect to ground decreasing the current flowing n in the vacuum tube 33 and applying a positive voltage to the output terminals and load. The amplifier thus reverses the polarity of a voltage applied to the input circuit.

A resistor 25 may be connected from the anode of vacuum tube 33 to the control grid of vacuum tube 3|. If a source of positive voltage 31 be connected, through a resistor 23 to the control grid of vacuum tube 3|, this source will tend to cause a current to flow through resistor 23, resistor 25, and anode-cathode path of vacuum tube 33 back to the source. plified positive voltage on the control grid of vacuum tube 33 will cause the anode current of vacuum tube 33 to increase to carry the current flowing in resistor25 and will produce a negative voltage across the output circuit equal to the voltage drop in the resistor 25. If the voltage amplification of the amplifier is large, this current will attain a value such that all the voltage of the source 31 is used to force the current through the resistor 23, reducing the potential difierence between the control grid of vacuum tube 3| and ground substantially to zero. The input circuit of the amplifier, from the control grid of vacuum tube 3| to ground, will appear to be of low impedance.

Under these conditions, as the same current flows in resistors 23 and 25, the voltage of the source 31 will be to the output voltage as the resistance of resistor 23 is to the resistance of resistor 25; in other words, the voltage gain for the source 31 is the ratio of the resistances of the resistors 25 and 23.

If the source 31 applies a negative voltage to the control grid of vacuum tube 3| the direction of current fiow through source 31, and resistors 23, 25 will be reversed, but the same gain and polarity relationships will be produced.

If a second source of a positive voltage 38 be connected through resistor 33 to the control grid of vacuum tube 3|, this source will also tend to cause a current to flow in resistor 25. The output voltage will rise, increasing the voltage drop in resistor 25 until the potential difierence between the control grid of vacuum tube 3| and ground is reduced substantially to .zero. The output voltage will then be equal to the voltage drop in resistor 25 due to the algebraic sum of the currents from the two sources. The voltage gain for the voltage from the source 38 is the ratio of the resistances of the resistors 25 and 39, and

The am-- is independent of the gain fo'r'the source 31. The output voltage is the algebraic sum of the amplified voltages from the sources 31, 38.

Let a capacitor be connected between the source 31 and resistor 23, then an increasing positive voltage from the source 31 will cause a cur-- rent to flow towards the control grid of vacuum tube 3| and will produce a negative output volt-- age proportional to the derivative or time rateof change of the applied voltage multiplied bythe ratio of the resistances of resistors 25 and 23. A decreasing positive voltage from the source 31 will cause a current to flow from the control grid of vacuum tube 3| and will produce a posi-- tive output voltage; an increasing negative voltage from the source 31 will cause a current to flow from the control grid of vacuum tube 3| and will produce a positive output voltage; a decreasing negative voltage from the source 31 will cause a current to-flow towards the control grid of vacuum tube 3| and will produce a negative output voltage. 3

In Fig. 1, the resistances of resistors 23, 25 arei selected so that the voltage selected by the brush of potentiometer 22 is reversed in polarity but; unchanged in magnitude. The positive voltage from the output of amplifier 24 is applied to a tap in the potentiometer winding 40. The negative voltage selected by the brush of potentiome ter 22 is applied to a tap in the winding 40 dia-' metrically opposite to the first tap. The equidistant, intermediate taps of the winding 40 are grounded.

The brushes 4|, 42 are located at right angles. and insulated from the shaft l3 and from each other. Assuming zero azimuth at the left-hand. grounded tap of the winding 40 and clockwise. rotation of the brushes 4| 42 for increasing azimuth, the brush 4| will select a voltage proportional to the positive sine of the azimuth: ATQ and brush 42 will select a voltage proportional to the positive cosine of the azimuth ATO- But, as shown in Fig. 2, the azimuth ATO equals 270 A, thus sin ATO equals cos A and cos ATO equals sin A. As the voltage selected by the brush of potentiometer 22 is proportional to 0T0, the voltage selected by brush 4| will be proportional to OTO cos A, that is the minus a: coordinate Om; and the voltage, selected by the brush 42 will be proportional to -OT0 sin A, that is, the minus y coordinate Tom.

The voltages selected by the brushes 4|, 42 are thus proportional to the rectangular co-- ordinates of the present position of the target with respect to the point of observation. These voltages may be converted into voltages proportional to the rectangular coordinates of the present position of the target with respect to the gun,. by adding thereto voltages proportional to the gun parallax, that is, the rectangular coordinates of the gun with respect to the point of observa tion.

The voltage selected by the brush 4| is applied through resistor 43 to the input circuit of an amplifier 44, of the type shown in Fig. 7, having a feedback resistor 45. A source of voltage 46,

having an intermediate point grounded, is connected across the winding of a potentiometer 41. The brush of potentiometer 41 is adjusted to select a voltage proportional to the a: coordinate of the gun with respect to the point of observa-- tion, which is applied through resistor 48-to the input circuit of the amplifier 44. The outputvoltage of amplifier 44 will then be proportional to I-Xo, the coordinate of the target with respect to the gun.

The output voltage of amplifier 44 is applied through capacitor 49 and resistor 50 to the input circuit of an amplifier of the type shown in Fig. '7, having a feedback resistor 52.

As the brush 4| is rotating clockwise for increasing azimuth, the voltage selected by the brush 4| is increasing. Thus, the positive output voltage of amplifier 44, applied to capacitor 49, is increasing. The output voltage of amplifier 5| will thus be of negative polarity with respect to ground, and proportional to X, the time derivative of X0, or the speed of the target in the direction of the X axis.

The output circuit of the amplifier 5| is connected to a smoothing network 53, which may be of the type shown in Fig. 6.

The network shown in Fig. 6 includes the series resistors 6|, 62, shunt capacitors 63, 64 and the bridged T section formed by series resistors 65, 56, bridged by capacitor 69, and shunt arm comprising resistor 61 and capacitor 68. The complete network produces a smoothed weighted average of the applied values of X.

The network 53 is connected to the input circuit of an amplifier 54 having a feedback resistor 55. The output of amplifier 54 will then be proportional to +X.

The voltage selected by the brush 42 is similarly combined with the voltage selected by the brush of potentiometer 48', to produce a voltage from the output of amplifier 44' proportional to +Yo. The output circuit of amplifier 44 is connected through capacitor 49' to the input circuit of amplifier 5|. As the brush 42 is rotating clockwise for increasing azimuth, the voltage selected by the brush 42 is decreasing. Thus, the positive output voltage of amplifier 44' applied to capacitor 49 is decreasing. The output voltage of amplifier 5| will thus be of positive polarity. The output circuit of amplifier 5| is connected through network 53' to the input circuit of amplifier 54'. The output voltage of amplifier 54 will thus be proportional to Y, the time derivative of Y0, or the speed of the target in the direction of the Y axis. Under the conditions shown in Fig. 2, the target is moving in the direction which decreases the Y coordinate, thus the speed of the target in this direction is negative.

Elements in the channel connected to brush 42 having similar functions to the elements in the channel connected to brush 4| have similar reference characters, distinguished by a prime.

Thus, the voltages with respect to ground of the connections 56, 51, 58, 59, are respectively proportional to +X, +XQ, +Yo and Y.

If the gun is fired at the instant that the target passes through To, Fig. 2, the shell will take a time, TF, the time of flight, to travel from the gun G to Tp, the predicted position of the target. During this time interval, the change DX in the x coordinate of the position of the target, that is, the distance T00, Fig. 2, will be X.TF; and the change DY in the y coordinate, that is,

the distance TpC, Fig. 2, will be Y.TF. The predicted position of the target will then have the coordinates X0+XTF and YOYTF.

In some cases, the data transmission system may be disabled, and only the values, telephoned at regular intervals, are available at the computer. These data are of a time in the past equal to the average time interval, TD, required by the operator to set in the data, which may be called the dead time. In some cases, the pre-- dicted position of the target will have the coordinates X +X(TF+TD) and Y0Y(TF+TD). The value of TF is, as yet, unknown and must be determined by the computation.

Connection 56 is connected through the winding of potentiometer 13 to ground. The brush of potentiometer 13 is moved, as explained hereinafter, to select a voltage proportional to +XTF, and is connected, by connection 14 and resistor 15 to the input circuit of amplifier 1|, of the type shown in Fig. 7, having a feedback resistor 12. The gains of amplifiers 5|, 54, Fig. 1, are adjusted so that the change XTF has the same scale of yards per volt as X0.

Connection 51, Fig. 3, is connected through resistor 218 to the input circuit of an amplifier 219, of the type shown in Fig. '7, having a feedback resistor 280.

Connection 56 is connected through the winding of potentiometer 16 to ground. The brush of potentiometer 16 is adjusted to select a voltage proportional to XTD. The brush of potentiometer 16 is connected through resistor 11 to the input circuit of amplifier 219. The output voltage of amplifier 219 will then be proportional to (Xo-I-XTD).

The output circuit of amplifier 219 is connected through resistor I8| to the input circuit of the polarity reversing amplifier I82, of the type shown in Fig. 7, having a feedback resistor I83. The output voltage of amplifier I82 will be proportional to +Xo+XTD.

The output circuit of amplifier I82 is connected by connection 284 through resistor 10 to the input circuit of amplifier 1|.

. The output circuit of amplifier 1| is connected to the lower tap of potentiometer winding 18, and, through the polarity reversing amplifier 19, of the type shown in Fig. 7, to the diametrically opposite upper tap. Intermediate, equidistant taps of the winding 18 are grounded. The Winding 18 has a sinusoidal variation of resistance.

Connection 58 is connected through resistor 28| to the input circuit of an amplifier 282, of the type shown in Fig. 7, having a feedback resistor 283.

Connection 59 is connected through the winding of potentiometer 86 to ground. The brush of potentiometer 86 is adjusted to select a voltage proportional to YTD and is connected through resistor 81 to the input circuit of amplifier 282. The gains of amplifiers 5|, 54' are adjusted so that YTD has the same scale of yards per volt as Y0. The output voltage of amplifier 282 will then be proportional to Yo +YTD. The output circuit of amplifier 282 is connected through resistor I to the input circuit of a polarity reversing amplifier I86, of the type shown in Fig. 7, having a feedback resistor I81. The output circuit of amplifier I86 is connected by connection 285, through resistor 88 to the input circuit of amplifier 8|.

Connection 59 is connected through the winding of potentiometer 83 to ground. The brush of potentiometer 83 is moved by shaft I36 to select a voltage proportional to YTF and is con nected by connection 84 through resistor 85 to the input circuit of amplifier 8 I.

The output voltage of amplifier 8| is proportional to Yp, the Y coordinate of the predicted position of the target.

The output circuit of amplifier 8| is connected directly to the lowest tap in the potentiometer winding 88, and, through a polarity reversing amplifier 88, of the type shown in Fig. 7, to a diametrically opposite tap. The intermediate, equidistant taps of winding 88 are grounded.

In Fig. 2, let the coordinates of the point T: be XI and Yr.

X; sin BYf cos B= X cos AF-i-Y; sin AF=0 But Thus

(XpSD cos AF) cos AF+ (Y +SD sin AF) sin AF=0 -Xp cos AF+Yp sin AF-i-SDzO. (4)

The brush 9I is connected through a resistor- 95 to the input circuit of an amplifier 96 having a feedback resistor 91. The brush 93 is connected through resistor 98 to the input circuit of amplifier 96.

As explained hereinafter, a source of voltage proportional to +SD is connected to resistor 99.

The output voltage of the amplifier 98 will thus be proportional to +Xp cos AFYp sin AF-SD.

The output circuit of amplifier 90 is connected by connection I00 to a phase controlling network IOI, of the type shown in Fig. 5. One phase of a two-phase source of power I02 is also connected to the phase controlling network IOI and the other phase of the two-phase source is connected to one phase winding of a two-phase motor I03. The output of the phase controlling network IOI is connected to the other phase winding of the two-phase motor I03.

The phase controlling network of Fig. in-

cludes an input transformer I04 connected to one phase of the source of supply, an output transformer I05 connected to one phase winding of the motor and a bridge made up of the elements I06, I01, I08, I09, the conjugate vertices of the bridge being respectively connected to the transformers I04 and I05. The elements I06, I01, I08, I09 are equal non-linear resistors, such as copper-copper-oXide couples. When no current is supplied by the connection I00, the bridge is balanced, no power is transmitted by the network and the motor is at rest. When current of one polarity is supplied by the connection I00,

the bridge is unbalanced and power of one phase angle is supplied to the motor, causing the motor to rotate in one direction. When current of the opposite polarity is supplied by the connection I00, power of another phase angle is supplied to the motor, causing the motor to rotate in the opposite direction.

Thus, in Fig. 3, if the output of the amplifier 96 is not zero, the motor I03 will run, rotating the shaft 94 until the output of amplifier 96 is zero. Equation 4 is thus satisfied, and shaft 94 has rotated to the correct azimuth AF.

In Fig. 2, let Rj=Rv+SR, then Xf=Rj 005 B 10 and Yf=Rf sin B, thus, Xp'=R1 cos BSD sin B and Yp=Rf sin B+SD cos. B.

Hence Xp=-Rf sin AF+SD cos AF Yp=-Rf cos AF-SD sin AF Multiplying by sin AF and cos AF, respectively, and adding X sin AF+Yp cos AF -R; (5)

In Fig. 3, brush selects a voltage proportional to +Xp sin AF and is connected through resistor -IIO to the input circuit of an amplifier III, of

the type shown in Fig. 7, having a feedback resistor H2. Brush 92 selects a voltage proportional to +Yp cos AF and is connected through resistor II3 to the input circuit of amplifier III.

The output voltage of amplifier III will thus be proportional to +Rr.

At regular intervals, data is sent to the computer giving the weighted average value of the magnitude of the wind and the bearing, measured from north clockwise, of the direction from which the wind is blowing.

In Fig. 2, let wG be the wind vector of magnitude W at a bearing BW. Angle B=2'10AF and angle C=90BW.

In the present computer, a ballistic effect which produces a decrease in range is represented by a negative voltage and an effect which tends to drift the shell to the left is represented by a positive voltage.

The cross-wind CW is represented by the vector wn.

OW=W sin (B-C) =W sin (270AF-90+BW) =W sin (AFBW) =W (sin AF cos BWcos AF sin BW) (6) The range wind is represented by the vector nG.

In Fig. 3, a source of voltage 210, with midpoint grounded, has the positive pole connected vto the upper tap in a potentiometer winding 21I and the negative pole connected to the lower diametrically opposite tap, the equidistant, in-

termediate taps being grounded. The potentiometer winding 21I has a sinusoidal variation in resistance.

The brushes 2 12, 213, 214, 21s are mutually at right angles, insulated from the shaft 94 and from each other, and are rotated by the shaft 94 to the angle AF.

The brush 213 selects a voltage proportional to sin AF and the brush 215 selects a voltage proportional to sin AF. The brush 213 is connected to the upper tap of potentiometer winding II6, the brush 215 is connected to the diametrically opposite lower tap of winding H6, the

diametrically opposite lower tap of winding II1,

the intermediate, equidistant taps being grounded.

The brushes II8, I l9'are at right angles and insulated from each other and the shaft. Similarly, brushes I20, I2I are at right angles and through resistor I23 to connection I24. Theresistors I22, I23 reduce reactions between the circuits associated with brushes H8 and I20.

Brush II8 applies to connection I24 a voltage proportional to sin AF cos BW; and brush I20 applies to connection I24 a voltage proportional to cos AF sin BW. Connection I24 is connected to ground through the winding of potentiometer I25. The brush of potentiometer I25 is manually adjusted to the magnitude W of the wind. The voltage selected by the brush of potentiometer I25 will thus be proportional to W (sin AF cos BWcos AF sin BW), which, from Equation 6, is the cross-wind.

Brush H9 is connected through resistor I26, and brush I2I is connected through resistor I21 to connection I28. The resistors I26, I21 reduce reactions between the circuits connected to brushes H9 and I2I.

Brush II9 applies to connection I28a voltage proportional to sin AF sin BW; and brush I2I applies to connection I28 a voltage proportional to cos AF cos BW. Connection I28 is connected to ground through the winding of potentiometer I29. The brush of potentiometer I29 is manually adjusted to the magnitude W of the wind, and may be ganged with the brush of potentiometer I25. The voltage selected by the brush of potentiometer I29 will thus be proportional to W(sin AF sin BWcos AF cos BW) which, from Equation '7 is the range wind.

A source of voltage I30, with mid-point grounded, has the negative pole connected through resistor I3I to the brush of variable resistor I32; through resistor I33 to ground; and through resistor I34, connection I35 and resistor 99 to the input circuit of amplifier 9-6. The lower 'end of the winding of variable resistor I32 is grounded. The brush of variable resistor I32 is insulated from shaft I36 and is rotated by shaft I36, as explained hereinafter, proportionally to the quadrant elevation of the gun. The variable resistor I32 is in parallel with resistor I33 and the winding has a variation of resistance such that the voltage applied to connection I35 is proportional to the lateral correction for the drift of the shell.

The brush of potentiometer I25 is connected to one end of the winding of potentiometer I31, the other end 'being grounded. The brush of potentiometer I 31 is insulated from shaft I36, is rotated by shaft I36 proportionally to the quadrant elevation of the gun, and is connected through resistor I38 with connection I 35. The resistance of the winding of potentiometer I31 has a variation such that the voltage applied to connection I35 is proportional to the lateral correction for the cross-wind.

The voltage of connection I35 will thus be proportional to +SD, the sum of the deflection corrections and, as previously described, connection I35 is connected through resistor 99 to the input circuit of amplifier 96.

The output circuit of amplifier I I I is connected through resistor I39 to the input circuit of an amplifier I40, of the type shown in Fig. 7, having a feedback resistor I. The output voltage of amplifier I40 will be proportional to R1:. The output circuit of amplifier I40 is connected through resistor I42 to the input circuit of amplifier I43, of the type shown in Fig. 7, having a feedback resistor I44.

In Fig. 2, the range R: is the distance GT: and this range must be diminished by SR, the sum of the ballistic range corrections to give the range G'Tv to the virtual target, as the quadrant elevation must be the value which will direct the shell to the virtual target.

Ballistic effects which act to increase the required range have positive polarity, while effects which act to decrease the range have negative polarity. Thus, the effect RW, Equation 7, which is shown as a headwind is of negative polarity.

The wiper of potentiometer I29 is connected through the winding of potentiometer I45 to ground. The wiper of potentiometer I45 is rotated by shaft I36, but is insulated therefrom and is connected through resistor I46 to connection I 41.

If the projectile weight is greater than normal, switch I48 is set on the lower contact, connecting to the positive pole of source I30. If the weight is less than normal, switch I48 is moved to the upper contact connecting to the negative pole of source I30.

The lever of switch I49 is connected to ground through the winding of potentiometer I49 and through the winding of potentiometer I5I. The brush of potentiometer I49 is connected to ground through the winding of potentiometer I50. The brushes of potentiometers I50, I5I are respectively connected to connection I41 through resistors I52, I53, are manually adjusted to the setting for the projectile weight and may be ganged together.

If the temperature of the air is higher than normal, switch I54 is set on the lower contact connecting to the negative pole of source I30; if the temperature is below normal, switch I54 is -moved to the upper contact connecting to the positive pole.

The lever of switch I54 is connected to the brush of variable resistor I 55 and through the winding of potentiometer I56 to ground. The brush of potentiometer I56 is connected through resistor I51 to connection I41. The brush of resistor I55 is moved by shaft I36, and the brush of potentiometer I 56 is set to the value of the temperature.

If the muzzle velocity of the gun is above normal, switch I58 is set on the lower contact connecting to the positive pole of the source I30; if the muzzle velocity is below normal, switch I58 is moved to the upper contact connecting to the negative pole of the source I30.

The lever of switch I58 is connected through resistor I59 to the brush of variable resistor I60 and to the winding of potentiometer. I6I;. and through resistor I62 to the winding of potentiometer I63. The brush of resistor I60 is moved by shaft I36. The brushes of potentiometers I6I, I63 are respectively connected through resistors I64, I65 to connection I41, are set to the value 'of the muzzle velocity and may be ganged together.

If the density of the air is greater than normal, switch I66 is set on the upper contact connecting to the negative pole of source I30; if the density is less than normal, switch I66 is moved to the lower contact connecting to the positive pole of source I30.

The lever of'switch I66 is connected to :the brush of potentiometer I61 and through the winding of potentiometer I69 to ground. The winding of potentiometer I61 is shunted by a resistor I68. The brush of potentiometer I61 is moved by the shaft I36. The brush of potentiometer I69 is connected through resistor I19 to connection I41. v

Similar potentiometers may be controlledby shaft I36 to supply voltages to the connection I41 varying with other ballistic range effects, such as the height of site, earth rotation, etc.

The voltage with respect to ground of connection I41 will be proportional to SR, the sum of the ballistic range efi'ects. Connection I41 is connected through resistor I1I to the input circuit of amplifier I43.

The brush of variable resistor I12 is connected to the positive pole of source I39, through resistor I13 to ground and through resistors I14, I15 to the input circuit of amplifier I43.

The resistance of the winding of variable resistor I12 varies in such a way that the positive voltage applied to amplifier I43 varies with the functional relationship between range and quad rant elevation as given in the range tables for the particular gun and ammunition considered.

The output circuit of amplifier I 43 is connected to a phase controlling network I16, of the type shown in Fig. 5. A source of two-phase power I18 is connected directly to one phase winding of the two-phase motor I11 and, through the phase controlling network I16 to the other phase winding of the motor I11.

The negative voltages applied to the input circuit of amplifier through resistors I42, I1I are balanced by the positive voltage applied through resistor I15. If there is an unbalance, the output current of amplifier I43 unbalanoes the phase controlling network I16, starting motor I11 which rotates shaft I36 until balance is attained. The position of shaft I36 will indicate the quadrant elevation for the gun.

The cards for the windings of potentiometers I45, I49, I61 and variable resistors I55, I69 are shaped so that, combined with their respective associated networks, these elements will apply voltages to connection I41 varying in accordance with the respective functions as given in the range tables. The differences in the forms of the various circuits are found to reduce the amount of shaping of the cards required by the various functions. 4 Similarly, the cards of potentiometers 13, 83, I 31 and resistor I32 are shaped so that the proper voltage variations with quadrant elevation will be applied to the associated circuits.

In so far as the present invention is concerned, the above-described ap aratus, under the control of observations of the target. provides voltages proportional to the rectangular coordinates of the present position of the target and the predicted changes in the coordinates during the flight of the shell; voltages proportional to the firing range and ballistic deflection corrections; and a motion proportional to the firin azimuth. The present invention is not limited to the spe cific apparatus described above and may be embodied in any artillery director, or other coniputing system, mechanical or electro-mechanical," from which these, or analogous factors, may be obtained.

First method The output circuit of amplifier 219, Fig. 3, isv connected to the lower tap of a potentiometer winding I99, and the output circuit of amplifier I92is connected,totheuppr diametrically-op- "posite tab of; winding I99. The equidistant in- "termed'iate tops of winding I99 are grounded. 5 'f'ihe- 'winding I99 has a sinusoidal variation of resistance. I ""Theoutput circuit oi amplifier 292, Fig. 3 is connected to the lower tap of potentiometer winding 194, and the output circuit of amplifier ml-1,86 isconnected to the upper diametrically opposite tap" of winding I84. The equidistant intermediate tapsj of. winding I94 are grounded. The winding I84 has a sinusoidal variation of resistance. g 15 The brushes .166, 189, Ml are rotated by the shaft 94, are-insulatedirom the shaft 94 and each other, and respectively select voltages .proportionafto "+(XO+XTD)- sin AF, -(XO+XTD) cos AF and -(XO+XTD) sin AF.

The brushes I599, 'IQI, 2 92 are also rotated by the shaft 94, are insulated from the shaft 94 and each othe'if andrespectively select voltages proportional to". Yo-; YrD)- cos AF, +'(Yo-Y 1*D) sin AF, and -(Yo-j-YTD) cos AF. Nor m ally, the-dead time TD is zero,thus the terms XTD'andiTD are also zero.

Brush I99, Fig. 3; is connected by connection I92j1through resistor. I93, Fig. 4A, to the input circuit oi. amplifier 1'94, of the type shown in Fig. '1, having af'eedback resistor I95. Brush I9I is similarly connected by connection I96, through resistor I91, to the input circuit of amplifier I94. Brush I588, Fig.- 3,'is connected by connection 35 I99to the upper end of the winding of potentiometerI99, Fig. 4A. Brush 29I, Fig. 3, is 'ccm nected by connectionjpli -to the lower end of the winding of potentiometer I99. lhej mid-point of the winding of-poten'tiometer I99 isv grounded.

Bruslr 'I-99, Fig. 3,'--is connected by connection 293 tothe lower *end ofjthe windingof'potentiom'eterl" 294, Fig. 4A. Brush 292, Fig.3, is connected by connection 295 to the upper end of the winding 'off potentiometer 294. The -midpoint .-of the winding of potentiometer 294 is grounded.

The windings of potentiometers I99 and 294 vary in resistance" with a. tangent function. For vfairly slow targets, the deflection angle is usually less-than 1'0" degrees, thus, the variation in the findings n'ottoo-great.

' -{With'zero-a' :gleatithe mid-point 'of the winding and"'olocl:'wlse rotation for positive angles, the brush-fof potentiometer I99 wills'elect a voltage approximately proportional .to' -'tan- AD'Xo sin' AF, and-is connected through resistor -296 to. the inputcircuit of amplifier I94.

The brush ofpotentiometer 294 selects a voltage approximately proportional to tan ADYo 6 cos AE andIi'sfcQnnected through resistor 291 to .thei'nputcircuitofianiplifier I94.

" -The outputqcircuit,:ot.,amplifier I94 is connected to a phaseccntrolling network 298, of the tyDe;ShQWngin' Fig.'5 source of two phase icwerJ-299, ls -"connect d-i'dire'ctly to one phase -'winding of a. two-phase motor 2I9 and, through the phaseffcontrolling. network 298 to the other phase winding of motor 2J9. v The shaft of motor 2J9 rotates"the"brushes'yof potentiometers I99 and294.

i The voltage'ssuppIied to the amplifier -'I 94 are approximately equal to 'tanj AD-Xo'sin AF tan AD'Yo cos AF *Xo cos AF+YO sin 4F 7 andirom-Equatioii 1'. that of these voltages may be indicated on a dial 2| land is transmitted 10 continuously or at'intervals to; the gun crew.

' Seccndmethod I Connection I35, Fig. 3, has a potential :with respect to ground proportional tof-l-SD, the sum of the ballistic deflection effects and is connected -through resistor 2I3, Fi'g. 4B,' to" the input cir- -cuit of an amplifier 2I4, or the type shown in Fig. 7, having a feedback resistor 2 I 5.

Brushes I68 and I90, Fig-3, .arerespectively connected by connections I 99 and Milt-through fresistors 2I9, 216, .Fig. tB to the 'upper ,end of ,thewinding of potentiometer 22,0, Brushes'iZ OI, 202, Fig. 3, are respectivelyjconnected by "connections 200 and'205 through resistors 2'I1';-2'I 8, Fig.- 43, with the lower end of :thewinding of potentiometer 220. The"mid"-point "of the winding of potentiometer 220 iS'gIOllIlded, and the winding varies in resistance with a tangent function. The resistors 2I6, 2'I1,.2I8, 2.I9- reduce interactions betweenthe connected circuits.

Connection 14, Fig. 3, which has a voltage with respect to ground proportional to DX, the predicted change in the X coordinate, isconnected to the upper tap of potentiometer winding 22'I,'and through resistor 222 to the input circuit ofan amplifier 223, of the type shown in Fig'f'l', having a feedback resistor 224. The outputcircuit of amplifier 223 is connected to the lower diametrically opposite tap of potentiometer winding 22 I, l

the intermediate, equidistant taps of winding 22I being grounded. Winding -22I =has"'a sinusoidal variation of resistance. I r I Connection 84,-Fig. 3, which has a voltage with respect to ground proportional't'o DY, the'prew dicted change in the Y coordinate,is connected to the upper tap of potentiometer winding 225 and is also connected through resistor 226 to the input circuit of an amplifier 221, of the type shown in Fig. 7, having a feedback resistor 228. The output. N

Brushes 229, 230, 23: are-rotatedby shaft/ 94,

16 245 is connected directly to one phase winding of a two phase motor 246, and, through the phase controlling network 244 to the other phase winding of motor 246.

The brush of potentiometer 220 selects a voltage approximately proportional to +tan AD(X0 sin AF+YO cos AF)v thus the voltages supplied to the input circuit of +SDDX cos AF+DY sin AF+ tan insulated from shaft 94 and each other, ."and' respectively select voltages proportional to DX cos AF, +DX sin AF'and -DX sin AF.

Brushes 232, 233, 234 are rotated byshaft 94,- insulated from shaft and each other; andresp'ectively select voltages-proportional to {e-DYI cos AF,

"shown in Fig. 5. A source of two phase power.

AD X0 sin AF-l-Yo cos AF) and, from Equation 2 the sum of these voltages should be zero. If the sum of these voltages is not zero, current will flow from the output circuit of amplifier 2| 4 to the network 244 starting motor 246 to rotate the brush of potentiometer 220 until the sum is zero and the brush of potentiometer 220 has been rotated through the angle AD. The angle may be indicated on the dial 249 and is transmitted to the gun crew.

In class II firing, the target is tracked by a gun sight mounted on, or associated with, the gun, so as to turn in azimuth with the gun. The axis of the gun sight is inclined to the line of fire by the ,defiection angle. As the sight is aligned on the 'target at the instant the gun is fired, no correc- 'tion for dead time is necessary, thus none is in- :cluded in the values of DX and DY.

Third method Connection I35 has a potential with respect to ground proportional to SD and is connected ,through resistor 250, Fig. 40, to the input circuit ,of an amplifier 25I, of the type shown in Fig. '1, .having a feedback resistor 252. Connection 235 has a potential with respect to ground proportional to DX cos AF and is connected through resistor 253 to the input circuit .of amplifier 25I.

Connection 239 has a potential with respect to .ground proportional to +DY sin AF and is connected through resistor 254 to the input circuit The output of amplifier III, Fig. 3, has a potential with respect to ground proportional to +Rr and is connected by connection 255 to the upper end of the winding of potentiometer 251, Fig. 4C.

The output of amplifier I40, Fig. 3, has a potential with respect to ground proportional to Rr and is connected by connection 256 to the ,lower end of the winding of potentiometer 251,

Fig. 4C.

The mid-point of the winding of potentiometer 251 is-grounded and the resistance of the winding 'Varies with a tangent function.

The brush of potentiometer 251 will select a .voltage with respect to ground approximately proportional to R; tan AD and is connected .through resistor 258 to the input circuit of amplifier 25L Brushes 230, 234, Fig. 3, are respectively connected by connections 236, 240 through resistors 26I, 262, Fig. 40, to the lower end of the winding .of potentiometer 263. Brushes 23I, 232, Fig. 3, .are respectively connected by connections 231, 238 through resistors 259, 260, Fig. 40, to the up- 'per end of the winding of potentiometer 263. The mid-point of the winding of potentiometer 263 is grounded and the resistance of the winding varies with a tangent function.

The brush of potentiometer 263 will select a voltage with respect to ground approximately proportional to tan AD (ox sin AF-l-DY cos AF) and is connected through resistor 264 to the input circuit of amplifier 251.

The output circuit of amplifier 251 is connected to a phase controlling network 265, of the type shown in Fig. 5. A source of two-phase power 266 is connected directly to one phase winding of a two-phase motor 261, and, through the phase controlling network 265 to the other phase winding of motor 261.

The voltages supplied to amplifier 251 are approximately proportional to R; tan AD-tan AD(DX sin AF-l-DY cos AF) SD-DX cos AF+DY sin AF and from Equation 3 the sum of these voltages should be zero. If the sum is not zero, current will flow from the output circuit of amplifier 251 to the network 265, starting motor 261 which rotates the brushes of potentiometers 251, 263 till the sum of the voltages is zero. The position of the brushes of potentiometers 251, 263 will indicate the angle AD, which may be shown by dial 268, mounted on the shaft of motor 261.

The resistors 218, 211, 218, 219, Fig. 4B and 259, 260, 261, 252, Fig. 4C reduce interactions between the associated circuits. While two tan AD potentiometers are shown in Figs. 4A and 4C, one potentiometer may be used, if the associated circuits are suitably combined. In general, it is difiicult to combine a number of circuits through decoupling resistors to a single circuit and still keep the reactions between the circuits to a low valueyparticularly if the normal voltage of one circuit is much larger than the normal voltages of the other circuits.

The operations of the servo-motors 103, 111, Fig. 3,and 210, Fig. 4A, 246, Fig. 4B or 251, Fig. 4C, may be stabilized by known means, such as connecting a capacitor, or a capacitor in series with a resistor across the feedback path of the control amplifier, for example, from the mid-points of the resistors 91, 144, Fig. 3, 195, Fig. 4A, 215, Fig. 4B, 252, Fig; 40, to ground.

What is claimed is:

1. In a system for indicating the deflection angle between the vertical plane containing the line from a gun to the present position of a target and the vertical plane containing the line of fire of the gun, a source of voltage, means connected to said source and controlled in accordance with observations of the position and movement of the target to fractionate the voltage from said source to produce a first voltage proportional to the rectangular coordinate of the target with respect to the g'un along an arbitrary axis and a second voltag oportional to the rectangular coordinate of the get with respect to the gun normal to said a 5 conversion means connected to said controlled means and energized by said voltages to produce a third voltage proportional to the rectangular coordinate of the target with respect to the gun along the line of fire and a fourth voltage proportional to the rectangular coordinate of the target with respect to the gun normal to the line of fire, a potentiometer having a winding varying in resistancewith a tangent function connected to said conversion means and energized by said third voltage and a brush, a motor driving said brush, summing means connected from said conversion means and said brush to said motor to oppose said fourth voltage by the voltage 18 selected by said brush, whereby in driving said brush to make the difference of said voltages zero the motor is rotated to said deflection angle, and an indicator driven by said motor.

2. In a system for indicating the deflection angle between the vertical plane containing the line from a gun to the present position of a target and the vertical plane containing the line of fire of the gun, a source of energy, means connected to said source and controlled in accordance with observations of the position and movement of said target to draw from said source a first quantity of energy proportional to the rectangular coordinate of said target with respect to said gun along an arbitrary axis and a second quantity of energy proportional to the rectangular coordinate of said target with respect to said gun normal to said axis, conversion means connected to said controlled means and energized by said quantities of energy to produce a third quantity of energy proportional to the rectangular coordinate of said target with respect to said gun along the line of fire, and a fourth quantity of energy proportional to the rectangular coordinate of said target with respect to said gun normal to the line of fire, means connected to said conversion means for controllably fractionating said third quantity of energy in accordance with a tangent function, summing means connected to said conversion means and said fractionating means to oppose said fourth quantity of energy by said fractionated quantity of energy, and a motor connected to said summing means and driving said fractionating means to make the difference of said fourth and said fractionated quantities of energy equal zero, whereby said motor is rotated proportionally to the deflection angle, and an indicator driven by said motor.

3. In a system for indicating the deflection angle between the line from a gun to the present position of a target and the line of fire of said gun, a first means controlled in accordance with I gun, a second means connected to said first means and controlled in accordance with said observations to produce second and third voltages respectively proportional to the components of said a: coordinate perpendicular to and in the line of fire, a third means controlled in accordance with said observations to generate a fourth voltage proportional to the y coordinate of said present position, a fourth means connected to said second means and controlled in accordance with said observations to produce fifth and sixth voltages proportional to the components of said y coordinate perpendicular to and in the line of fire, adjustable means connected to said second and fourth means for attenuating said third and sixth voltages proportionally to a tangent function, thermionic means connected to said second, said fourth and said adjustable means to algebraically add said second, and said fifth voltages and said attenuated voltages, and a motor connected to said thermionic means and adjusting said adjustable means to make the sum of said voltages zero.

4. In a system for indicating the deflection angle between the line from a gun to the present position of a moving target and the line of fire of a shell directed to the predicted position of said target, a first means controlled in accordance with observations of said target to generate a first and a second voltage respectively proportional to 19 the x and y coordinates of the present position of said target with respect to said gun, a second means connected to said first means and controlled in accordance with said observations to produce third and fourth voltages respectively proportional to the components of said as and y coordinates in the line of fire, adjustable means connected to said second means to attenuate said third and fourth voltages in accordance with a tangent function, a third means controlled in accordance with said observations to generate a fifth voltage proportional to the lateral ballistic corrections for said shell, a fourth means controlled in accordance with said observations to generate sixth and seventh voltages respectively proportional to the components perpendicular to the line of fire of the predicted changes in said a: and y coordinates, thermionic means connected to said adjustable means and said third and fourth means to subtract said fifth, sixth and seventh voltages from the sum of said attenuated voltages and a motor connected to said thermionic means and adjusting said adjustable means to make the difference of said voltages zero whereby the position of said adjustable means indicates said deflection angle.

5. In a system for indicating the deflection angle between the line from a gun to the present position of a moving target and the line of fire of a shell directed to the predicted position of said target, a first means controlled in accordance with observations of said target to generate first and second voltages respectively proportional to the predicted changes in the x and y coordinates of said target during the time of flight of said shell, a second means connected to said first means and controlled in accordance with said observations to produce third, and fourth voltages respectively proportional to the components of said changes perpendicular to the line of fire, and fifth and sixth voltages respectively proportional to the components of said changes in the line of fire, a source of a seventh voltage proportional to the firing range of said shell, a third means connected to said second means and said source to attenuate said fifth, sixth and seventh voltages in accordance with a tangent function, a second source of an eighth voltage proportional to the lateral ballistic corrections for said shell, thermionic means connected to said second and third means and said second source for subtracting said third, fourth and eighth voltages from said attenuated voltages and a motor connected to said thermionic means and adjusting said adjustable means to make the difference of said voltages zero whereby the position of said adjustable means indicates said deflection angle.

6. In a system for producing a movement proportional to the deflection angle between the vertical plane containing the line from a gun to the present position of a target and the vertical plane containing the line of fire of the gun, a shaft, a source of energy, computing means connected to said source and controlled in accordance with observations of the position and movement of the target to supply from said source a first quantity of energy proportional to the rectangular coordinate of said target with respect to said gun normal to an arbitrary axis, a second quantity of energy proportional to the rectangular coordinate of said target with respect to said gun along said axis, a third quantity of energy proportional to the rectangular coordinate of the line of fire of the gun, and to rotate said shaft proportionally to the azimuth angle between the vertical plane containing said axis and the vertical plane containing the line of fire, first means connected to said computing means and driven by said shaft to fractionate said first quantity of energy proportionally to the sine of said azimuth angle, and to fractionate said second quantity of energy proportionally to the cosine of said azimuth angle, second means connected to said first means for controllably fractionating the sum of said fractionated quantities of energy in accordance with a tangent function, summing means connected to said computing means and said second means to oppose said third quantity of energy to said fractionated energy, and a motor connected to said summing means and driving said second means to make the difference of said third and said fractionated quantities of energy equal zero, whereby said motor is moved proportionally to the deflection angle.

7. In a system for producing a movement proportional to the deflection angle between the vertical plane containing the line from a weapon to the present position of a target and the vertical plane containing the line of fire of the weapon, a shaft, a source of voltage, computing means connected to said source and controlled in accordance with observations of the position and movement of the target to supply from said source a first voltage proportional to the rec tangular coordinate of said target with respect to said Weapon normal to an arbitrary axis, a second voltage proportional to the rectangular coordinate of said target with respect to said weapon along said axis, a third voltage proportional to the rectangular coordinate of said target with respect to said Weapon normal to the line of fire of the Weapon, and to rotate said shaft proportionally to the azimuth angle between the vertical plane containing said axis and the vertical plane containing the line of fire, first means connected to said computing means and driven by said shaft to fractionate said first voltage proportionally to the sine of said azimuth angle, and to fractionate said second voltage proportionally to the cosine of said azimuth angle, second means connected to said first means for controllably fractionating the sum of said fractionated voltages in accordance with a tangent function, summing means connected to said computing means and said second means to oppose said third voltage to said fractionated voltage and a motor driving said second means to make the output of said summing means equal zero, whereby said motor is moved proportionally to said deflection angle.

8. In a system for producing a movement proportional to the deflection angle between the vertical plane containing the line from a gun to the present position of a target and the vertical plane containing the line of fire of the gun, a shaft, a source of energy, computing means connected to said source and controlled in accordance with observations of the position and movement of the target to supply from said source first and second quantities of energy respectively proportional to the predicted changes during the time of flight of the shell in the rectangular coordinates of the position of the target with respect to said gun normal to and along an arbitrary axis, a third quantity of energy proportional to the correction for the differential ballistic effects normal to the line of fire, and a fourth quantity said target with respect to said gun normal to of energy proportional to the rectangular coor- 21 dinate of said target with respect to the gun normal to the line of fire of the gun, and to rotate said shaft proportionally to the azimuth angle between the vertical plane containing said axis and the vertical plane containing the line of fire, first means connected to said computing means and driven by said shaft to respectively fractionate said first and second quantities of energy proportionally to the cosine and the sine of the azimuth angle, second means connected to said computing means for controllably fractionating said fourth quantity of energy in accordance with a tangent function, summing means connected to said computing means and said first and second means to oppose the sum of said third quantity of energy and said fractionated first and second quantities of energy to said fractionated fourth quantity of energy, and a motor connected to said summing means and driving said second means to make the output of said summing means zero, whereby said motor is moved proportionally to the deflection angle.

9. In a system for producing a motion proportional to the deflection angle between the vertical plane containing the line from a weapon to the present position of a target and the vertical plane containing the line of fire of the Weapon, a shaft, a source of voltage, computing means connected to said source and controlled in accordance with observations of the position and movement of the target to supply from said source first and second voltages respectively proportional to the predicted changes during the time of flight of the shell in the rectangular c0- ordinates of the position of the target with respect to the weapon normal to and along an arbitrary axis, a third voltage proportional to i the correction for the differential ballistic effects 22 normal to the line of fire, a fourth voltage proportional to the rectangular coordinate of said target with respect to the weapon normal to the line of fire, and to rotate said shaft proportionally to the azimuth angle between the vertical plane containing said axis and the vertical plane containing the line of fire, first means connected to said computing means and driven by said shaft to respectively fractionate said first and second-voltages proportionally to the cosine and the sine of said azimuth angle, second means connected to said computing means for controllably fractionating said fourth voltage in accordance with a tangent function, summing means connected to said computing means and said first and second means to oppose the sum of said fractionated first and second voltages and said third voltages to said fractionated fourth voltage, and a motor connected to said summing means and driving said second means to make the output of said summing means zero, whereby said motor is moved proportionally to said deflection angle.

EMORY LAKATOS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,408,081 Lovell et al Sept. 24, 1946 2,426,658 Wooldridge Sept. 2, 1947 2,432,504 Boghosian et al. Dec. 16, 1947 FOREIGN PATENTS Number Country Date 164,765 Great Britain June 23, 1921 

